1. Field of the Invention
The present invention relates to a portable radio device such as a portable telephone for a mobile communication system, and particularly to a portable radio device in which degradation of antenna functions during communication can be reduced.
2. Description of the Related Art
The development of mobile communication systems in recent years has underscored the importance of improving the performance of this type of radio device, one approach focusing on the improvement of antenna gain, antenna pattern, and other factors of antenna performance, and another focusing on various contrivances for storing an antenna for easier portability. For example, Japanese Patent Laid-open No. 175826/91 discloses a portable telephone constructed with a recess in the rear surface of the telephone body 1 for accommodating an antenna unit 21 which may be raised for use by rotating the antenna unit 180.degree. about a hinge member 31 and pulling an extendible whip antenna vertically up from the antenna unit. The antenna can accordingly be positioned considerably higher than the telephone body 1 during use. In Utility Model Laid-open Number 23810/88, the base of a rod antenna is attached to a coupling 4 on the main body of the portable telephone by way of a freely rotatable coupling member 5, the antenna being raised in a vertical direction for use and rotated down when not in use for easy portability. Similarly, Utility Model Laid-open No. 84935/84 discloses a construction in which a rod antenna 8 is attached in a freely rotatable manner to one side of the case 1 of a portable radio device and the case is further provided with a case lid that can be freely opened and closed with respect to the case body and that has a groove 11 on one side that can accommodate the rod antenna, the antenna being raised vertically for use and folded into the groove when not in use.
During use, the rod-shaped antenna such as the rod antenna or whip antenna employed in the above-described portable radio devices extends parallel to the console surface (front surface) of the case of the radio device. As a result, as radio devices become increasingly smaller, the user inevitably comes into closer proximity to the antenna, which is on the top of the case and extends parallel to the front surface of the case. Such a radio device consequently suffers from the drawback of seriously degraded antenna performance which prevents stable communication with another station.